NATURAL-CONVECTION HEAT-TRANSFER BETWEEN A UNIFORMLY HEATED CYLINDRICAL ELEMENT AND ITS RECTANGULAR ENCLOSURE

A numerical study of natural convection heat transfer from a uniformly heated horizontal cylinder placed in a large air-filled rectangular enclosure, is performed using a spectral element method. The enclosure walls are isothermal and the flow is assumed laminar and two-dimensional. Dynamics of the flow and the thermal behavior is studied at various heat fluxes applied to the cylinder. It is found that the mean Nusselt number, Nu(a), varies with Rayleigh number, Ra(a), according to a general correlation of the form Nu(a) = C1(Ra(a))C2, where C1 and C2 are empirical constants that depend on the chosen scale length a. The resulting correlation constants C2 are similar to previously published correlation constants based on experimental data. The highest heat transfer rates out of the enclosure occur at the top wall. For all examined heat fluxes, the maximum air velocity is at a distance of about nine cylinder diameters along the vertical centerline above the heated cylinder.